Osteoarthritis (OA) of the knee affects 10% of all adults and results in pain and limited functional abilities. OA of the knee has also been positively correlated with declines in knee joint proprioception, gait speed, and leg strength. Previous investigators have been able to slow or reverse these outcomes of OA in adults through isometric strength training. A limitation of these studies is that the improvements were specific to the joint angle trained, which may explain the limited changes observed in functional ability. Functional ability involves movement of a joint over a functional range. Isometric strength training improves the functioning of the muscle only at the joint angle at which training takes place. Dynamic strength training by non-OA subjects has been shown to improve muscle function over the entire training range of motion. Therefore, OA patients who engage in dynamic strength training may demonstrate reduced knee pain and improved functional ability when compared to OA patients who complete isometric strength training or no training. The specific aim of this study is: To compare the efficacy of 16 weeks of isometric versus dynamic strength training on knee pain and functional abilities among adults with knee OA. Secondary research questions will compare the effects of these two modes of strength training on knee joint proprioception, gait characteristics and quadriceps strength. 135 adults with knee OA will be recruited over the three year project. Subjects will be assessed regarding their knee pain, functional abilities, knee joint proprioception, gait characteristics, and quadriceps strength prior to and following a 16-week intervention. Following the initial testing subjects will be randomized into an isometric strength training group, a dynamic strength training group or a no-exercise control group. The strength training groups will engage in either isometric or dynamic strength training of the legs three times per week for 16 weeks. Analysis of covariance will determine the effects of group assignment over time on the dependent measures. The results of this study have the potential to improve OA patients' functional ability and reduce their pain through altering the type of exercise they are commonly prescribed.